Diseases and Health: Communicable, Non-Communicable, Vaccines & WHO

Disease and health questions appear in almost every Kerala PSC exam. This guide covers communicable and non-communicable diseases, causative agents, vaccines, epidemics, and WHO terminology — the exact pattern PSC tests.

Classification of Diseases

Type	Meaning	Examples
Communicable (Infectious)	Spread from person to person or through vectors	Tuberculosis, Malaria, COVID-19
Non-communicable	Cannot spread from person to person	Diabetes, Cancer, Heart disease
Deficiency diseases	Caused by lack of nutrients	Scurvy, Rickets, Beriberi
Genetic/Hereditary	Inherited through genes	Haemophilia, Sickle cell anaemia, Colour blindness
Degenerative	Due to ageing/wear of organs	Alzheimer’s, Osteoarthritis

Major Bacterial Diseases

Disease	Causative Bacterium	Transmission	Key Symptoms	Vaccine/Treatment
Tuberculosis (TB)	Mycobacterium tuberculosis	Airborne (droplets)	Persistent cough, weight loss, night sweats	BCG vaccine
Cholera	Vibrio cholerae	Contaminated water/food	Severe diarrhoea, dehydration	ORS, antibiotics; oral cholera vaccine
Typhoid	Salmonella typhi	Contaminated food/water	High fever, headache, abdominal pain	Widal test for diagnosis; TAB vaccine
Plague	Yersinia pestis	Rat flea bite	Swollen lymph nodes (bubonic), pneumonia (pneumonic)	Antibiotics
Leprosy (Hansen’s disease)	Mycobacterium leprae	Prolonged close contact	Skin patches, nerve damage	MDT (Multi-Drug Therapy)
Diphtheria	Corynebacterium diphtheriae	Airborne (droplets)	Sore throat, membrane in throat	DPT vaccine
Tetanus	Clostridium tetani	Wound contamination (soil)	Muscle spasms, lockjaw	TT (Tetanus Toxoid) vaccine
Pneumonia	Streptococcus pneumoniae (most common)	Airborne	Cough, fever, chest pain	Pneumococcal vaccine
Whooping cough (Pertussis)	Bordetella pertussis	Airborne	Severe coughing fits	DPT vaccine
Gonorrhoea	Neisseria gonorrhoeae	Sexual contact	Painful urination, discharge	Antibiotics
Syphilis	Treponema pallidum	Sexual contact	Painless sore (chancre), rash	Penicillin

Major Viral Diseases

Disease	Virus	Transmission	Key Symptoms	Vaccine/Treatment
Common cold	Rhinovirus	Airborne, contact	Sneezing, runny nose	No specific vaccine; symptomatic treatment
Influenza (Flu)	Influenza virus (A, B, C)	Airborne	Fever, body aches, cough	Flu vaccine (annual)
COVID-19	SARS-CoV-2	Airborne, droplets	Fever, cough, loss of taste/smell	Multiple vaccines (Covishield, Covaxin, etc.)
Measles	Measles virus (Paramyxovirus)	Airborne (highly contagious)	Rash, fever, Koplik spots	MMR vaccine
Mumps	Mumps virus (Paramyxovirus)	Airborne, saliva	Swollen parotid glands	MMR vaccine
Rubella (German measles)	Rubella virus	Airborne	Mild rash, dangerous in pregnancy	MMR vaccine
Chickenpox	Varicella-zoster virus	Airborne, contact	Itchy blisters all over body	Varicella vaccine
Poliomyelitis	Poliovirus	Faecal-oral route	Paralysis (in severe cases)	OPV (oral) / IPV (injectable)
Rabies	Rabies virus (Lyssavirus)	Animal bite (dog, bat)	Hydrophobia, aggression, fatal	Post-exposure prophylaxis; no cure once symptomatic
Dengue	Dengue virus (Flavivirus)	Aedes aegypti mosquito	High fever, joint pain, rash	No widely used vaccine; supportive care
Chikungunya	Chikungunya virus	Aedes mosquito	Fever, severe joint pain	No vaccine; supportive care
Hepatitis A	Hepatitis A virus	Faecal-oral (contaminated food/water)	Jaundice, fatigue	Hepatitis A vaccine
Hepatitis B	Hepatitis B virus	Blood, sexual contact, mother to child	Jaundice, liver damage, chronic	Hepatitis B vaccine (part of Universal Immunisation)
AIDS	HIV (Human Immunodeficiency Virus)	Blood, sexual contact, mother to child	Immune system destruction	No vaccine; ART (Antiretroviral Therapy)
Ebola	Ebola virus	Contact with body fluids	Haemorrhagic fever, very high mortality	rVSV-ZEBOV vaccine
Zika	Zika virus	Aedes mosquito, sexual contact	Mild fever; microcephaly in newborns	No vaccine

Protozoan Diseases

Disease	Causative Organism	Transmission	Key Symptoms
Malaria	Plasmodium (P. vivax, P. falciparum, etc.)	Female Anopheles mosquito	Cyclic fever, chills, anaemia
Amoebic dysentery	Entamoeba histolytica	Contaminated food/water	Bloody diarrhoea
Sleeping sickness	Trypanosoma brucei	Tsetse fly	Drowsiness, confusion
Kala-azar (Leishmaniasis)	Leishmania donovani	Sandfly bite	Fever, enlarged spleen, weight loss

Fungal Diseases

Disease	Causative Fungus	Affected Area
Ringworm	Trichophyton, Microsporum	Skin, nails, scalp
Athlete’s foot	Trichophyton	Feet (between toes)
Candidiasis	Candida albicans	Mouth (thrush), genital area
Aspergillosis	Aspergillus	Lungs

Worm Diseases (Helminthic)

Disease	Causative Worm	Transmission
Filariasis (Elephantiasis)	Wuchereria bancrofti	Culex mosquito
Ascariasis	Ascaris lumbricoides (roundworm)	Contaminated food/water
Taeniasis	Tapeworm (Taenia)	Undercooked meat

Vectors and Diseases They Transmit

Vector	Diseases
Female Anopheles mosquito	Malaria
Aedes aegypti mosquito	Dengue, Chikungunya, Zika, Yellow fever
Culex mosquito	Filariasis, Japanese encephalitis
Tsetse fly	Sleeping sickness
Sandfly	Kala-azar (Leishmaniasis)
Rat flea	Plague
Housefly	Cholera, Typhoid, Dysentery

Important Vaccines — Discovery and Schedule

Vaccine	Disease	Discoverer/Developer
Smallpox vaccine	Smallpox	Edward Jenner (1796) — first vaccine ever
BCG	Tuberculosis	Albert Calmette and Camille Guerin
OPV (Oral Polio)	Polio	Albert Sabin
IPV (Injectable Polio)	Polio	Jonas Salk
DPT	Diphtheria, Pertussis, Tetanus	Combination vaccine
MMR	Measles, Mumps, Rubella	Combination vaccine
Hepatitis B	Hepatitis B	Part of Universal Immunisation Programme

India’s Universal Immunisation Programme (UIP)

Diseases covered under UIP: Tuberculosis, Diphtheria, Pertussis, Tetanus, Polio, Measles, Hepatitis B, Pneumonia (Hib), Japanese Encephalitis (in endemic areas), Rotavirus diarrhoea (in some states), Rubella.

Deficiency Diseases

Nutrient Deficient	Disease	Symptoms
Vitamin A	Night blindness (Nyctalopia)	Cannot see in dim light
Vitamin B1 (Thiamine)	Beriberi	Nerve damage, weakness
Vitamin B3 (Niacin)	Pellagra	Dermatitis, diarrhoea, dementia (3 Ds)
Vitamin C	Scurvy	Bleeding gums, weakness
Vitamin D	Rickets (children) / Osteomalacia (adults)	Soft bones, bowed legs
Vitamin K	Haemorrhage	Bleeding disorders
Iron	Anaemia	Fatigue, pale skin
Iodine	Goitre	Swollen thyroid gland
Protein	Kwashiorkor	Swollen belly, muscle wasting (children)
Protein + Calories	Marasmus	Severe emaciation (children)

WHO Terminology

Term	Definition
Epidemic	Sudden outbreak of disease in a particular area, spreading beyond normal expectation
Pandemic	Epidemic that has spread across multiple countries or continents
Endemic	Disease constantly present in a particular region (e.g., Malaria in parts of India)
Sporadic	Disease occurring occasionally, irregularly
Zoonotic	Disease transmitted from animals to humans (e.g., Rabies, Avian flu)
Incubation period	Time between infection and appearance of symptoms
Quarantine	Isolation of people who may have been exposed to disease
Vector	Organism that transmits disease from one host to another
Pathogen	Organism that causes disease (bacteria, virus, fungus, protozoa)
Carrier	Person who harbours a pathogen without showing symptoms

World Health Organization (WHO) — Key Facts

Fact	Detail
Founded	April 7, 1948
Headquarters	Geneva, Switzerland
World Health Day	April 7
Parent body	United Nations
Current Director-General	Tedros Adhanom Ghebreyesus (since 2017)
Major campaigns	Smallpox eradication (1980), Polio eradication (ongoing)

Historic Epidemics and Pandemics

Event	Year	Cause	Significance
Black Death (Plague)	1347–1351	Yersinia pestis	Killed estimated 25–50 million in Europe
Spanish Flu	1918–1919	H1N1 Influenza	Estimated 50–100 million deaths worldwide
Smallpox eradication	Declared 1980	Variola virus	First disease eradicated by vaccination (WHO declared)
HIV/AIDS pandemic	1981–present	HIV	Over 40 million deaths to date
COVID-19 pandemic	2019–present	SARS-CoV-2	Declared pandemic by WHO on March 11, 2020

Frequently Asked PSC Questions

Q: Who discovered the first vaccine? A: Edward Jenner (smallpox vaccine, 1796)

Q: Which mosquito transmits Malaria? A: Female Anopheles mosquito

Q: Which mosquito transmits Dengue? A: Aedes aegypti

Q: BCG vaccine is for which disease? A: Tuberculosis

Q: Which vitamin deficiency causes Scurvy? A: Vitamin C

Q: Pellagra is caused by deficiency of? A: Vitamin B3 (Niacin) — remember the 3 Ds: Dermatitis, Diarrhoea, Dementia

Q: First disease to be eradicated by WHO? A: Smallpox (declared eradicated in 1980)

Q: Rabies virus is also known as? A: Lyssavirus

Q: Kala-azar is transmitted by? A: Sandfly

Exam Tips

• Memorize the Vector-Disease pairs — tested in every exam
• Know the difference between epidemic, pandemic, and endemic — PSC loves definitions
• Edward Jenner (smallpox) and Louis Pasteur (rabies vaccine, germ theory) are the two most tested scientists
• For Kerala-specific: Dengue and Chikungunya are common in Kerala; Nipah virus outbreaks have occurred in Kerala (2018, 2019, 2023)
• Vitamin deficiency table is a guaranteed question — learn all vitamins and their deficiency diseases